Mississippi River flood: US to open Louisiana gates - TheNewTopical.com - current events, politics, culture, ethics, economics discussion forum

FredFredson · #1 (**permalink**) 13-05-11, 08:10 PM

13 May 2011 Last updated at 10:56 ET

Mississippi River flood: US to open Louisiana gates

BBC News - Mississippi River flood: US to open Louisiana gates

The Morganza Floodway gates The Morganza Floodway was completed in 1954 and is 20 miles (32.2km) long and five miles wide

US engineers are preparing to flood up to three million acres in southern Louisiana in a bid to protect large cities along the Mississippi River.

The Army Corps of Engineers said it could open a floodway to divert water from the river this weekend. As many as 25,000 people are preparing to leave.

Opening the Morganza Floodway would ease pressure on levees protecting the cities of Baton Rouge and New Orleans.

The Mississippi River has risen to levels not seen in decades this year.

Fed by rainwater and the spring thaw, the river and its tributaries have caused massive flooding upstream, and officials have said the flooding in Louisiana is the worst since 1927.

If, as expected, the Army Corps of Engineers this weekend opens the Morganza floodway for the first time in 38 years, it will unleash Mississippi River water through the Atchafalaya River basin, flooding parts of seven parishes in southern Louisiana near the Gulf of Mexico.

Much of the water would end up in swamplands, bayous and backwater lakes but several thousand homes are at risk of flooding.

"My message to our people is they don't need to be delaying," Louisiana Governor Bobby Jindal said on Thursday. "Move their valuables. Think about where they would go."

Earlier this week, the Mississippi River flooded parts of Memphis, Tennessee, the city famed as one of the birthplaces of rock and roll and blues music.

Further upstream, the Army Corps of Engineers has opened floodways in Missouri to keep pressure off levees protecting the town of Cairo, Illinois.

The US government has said farmers whose land has been flooded will be reimbursed for destroyed crops.

FredFredson · #2 (**permalink**) 13-05-11, 08:18 PM

What I find interesting about this story is that the "Atchafalaya River basin" is actually the course the Mississippi would be flowing through NOW if the flood way had not been built back in the 50s. The Mississippi river is too long for it's flow rate, sediment load and slope. There is a mathematical relationship between the factors that determines the "length" a river will prefer to be.

The very broad meanders that characterize the lower reaches of the Mississippi often flow prodigious distances across the valley for very short up valley distance. Back in the steamboat days they found they could shorten the trip upriver by 40 miles with a thousand foot ditch between two meanders. This worked great until the river added back in the missing distance by meandering elsewhere!

Back in the 50s analysis of the Mississippi indicated that it was getting ready to switch back into the Atchafalaya River basin. It had flowed there thousands of years ago. So the Army Corp of Engineers built the flood way controls to keep it from doing just that.

The time is coming when the mighty Mississippi will do as it pleases and head to the sea via the shorter Atchafalaya River system. This years peak flow is exactly the kind of event which would naturally produce such a course shift.

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FredFredson · #3 (**permalink**) 13-05-11, 08:45 PM

Atchafalaya case history in river management.

Quote:

Quote from John McPhee, The Control of Nature: " The Mississippi River, with its sand and silt, has created most of Louisiana, and it could not have done so by remaining in one channel. If it had, southern Louisiana would be a long narrow peninsula reaching into the Gulf of Mexico. Southern Louisiana exists in its present form because the Mississippi River has jumped here and there within an arc about two hundred miles wide, like a pianist with one one hand -- frequently and radically changing course, surging over the left or the right bank to go off in utterly new directions. Always it is the river's purpose to get to the Gulf by the shortest and steepest gradient. ... By the nineteen-fifties, the Mississippi River had advanced so far past New Orleans and out into the Gulf that it was about to shift again, and its offspring the Atchafalaya was ready to receive it. By the route of the Atchafalaya, the distance across the delta plain was a hundred and forty-five miles -- well under half the length of the route of the master stream."

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Zichao · #4 (**permalink**) 13-05-11, 09:06 PM

Originally Posted by FredFredson

"My message to our people is they don't need to be delaying," Louisiana Governor Bobby Jindal

Awesome. A Louisiana Governor called Bobby saying things like "don't need to be delaying". So often things are nothing like how they're supposed to be, but this guy has clearly found his precise niche in life.

Incientally, I thought that the Mississippi was a bit like the Yangtze - left to its own devices it would fling itself back and forth across the landscape like a dropped fire hose, drowning multitudes as it went.